Resistor structure



Nov. 5, 1957 R. E. DU 5015 RESISTOR STRUCTURE Filed May 16, 1955 2 Sheets-Sheet 1 IIIIIIIF' INVENTOR ROBERT E. DUBOIS W/ZALM ATTORNEY Filed May 16, 1955 R. E. DU B018 2 Sheets-Sheet 2 mnlfllm,

25 u 2 I6 26 o INVENIOR ATTORNEY United States Patent RESISTOR STRUCTURE Robert E. DuBois, Hammond, Ind. Application May 16, 1955, Serial No. 508,431

1 Claim. (Cl. 201--69) This invention relates generally to electrical resistance structures and more specifically to the mounting structure for a reverse-folded zig-zag resistance unit.

The primary object of the invention is to provide an improved mount for a resistor grid unit which is temperature compensating in nature for preventing the warping or deformation of the grids when they become heated.

A more specific object of the invention is to provide a resistance structure in which the grid unit is freely mounted within the supporting frame to allow expansion or contraction of the unit within the frame with variations of temperature.

Another object of the invention is to provide a mounting frame for a resistor element which will allow vertical expansion of the resistor element when heated, but which will restrict any tendency toward lateral or longitudinal displacement of the element within the frame.

A further object of the invention is to provide a mounting frame for a resistor element which will allow distortion of the frame under torsional stress, shock, and vibration conditions while maintaining the resistor element rigidly constant and substantially free from said conditions of the frame.

With the foregoing, and other objects in view, the invention resides in the following specification and appended claim, certain embodiments and details of construction of which are shown in the accompanying drawing in which:

Figure 1 is a side elevational view of a typical resistor structure to which this invention is applied;

Figure 2 is a plan view of the resistor structure;

Figure 3 is a bottom view of the resistor structure;

Figure 4 is an end elevational view of the resistor structure;

Figure 5 is a sectional end elevational view of the resistor structure taken on line 55 of Fig. 2, showing the resistor grid supporting means; and

Figure 6 is a partial longitudinal sectional detail taken substantially on line 66 in Fig. 2, further showing the resistor grid supporting member.

Resistor grids expand and contract in service due to heating, and unless the connection to the mounting frame allows for this expansion, an unnecessary strain is set up in the grids, causing warping, breakage, and possible shortcircuiting. The prior art has allowed for this expansion of resistor grids in several ways, such as by loosely mounting the resistor grids to the supporting means, or by loosely mounting the supporting means to the resistor frame. This looseness permits a general deterioration and breakage of the entire resistor unit and its ceramic insulating tubes and washers under heavy vibrational strains.

The present invention provides a novel and economical means for overcoming the above difficulties encountered in the prior art.

Referring to Figures 1, 2 and 3, the grid unit 1, made of cast iron or any suitable alloy material is employed as the resistance unit in my invention. This resistance 2,812,410 Patented Nov. 5, 1957 unit is provided with reverse folds or loops, that is to say, it is folded back and forth in a zig-zag manner, although it may be of any desired configuration. The resistance unit is mounted in a frame shown generally at 2, consisting of channel-shaped end members 3 and 4 rigidly connected by grid supporting members shown generally at 5, 6 and 7. The frame may be of any desired construction, the exact detail of which is not pertinent to the present invention. Lead-in terminals 8 and 9, mounted upon supporting members 5 and 6 as shown in Fig. 5, are connected to the end of the resistance unit 1 to provide means for connecting the unit into an electrical system.

Referring to Figure 4, resistance unit 1, shown in dotted lines, is supported generally by grid supporting members 5, 6 and 7. As shown more clearly in Fig. 5, guide members or pins 11 and 12, welded or otherwise secured to the upper and lower portions of grid resistance unit 1, cooperate with grid support members 5, 6, and 7 to secure the grid unit within the structure. Pins 11 are closely fitted between members 5 and 6 so that there is no lateral movement or play. Similarly, pins 12 straddle member 7 with a close fit so that there is no lateral movement. It should be stressed that neither pins 11 or 12 are secured to grid supporting members 5, 6 and 7. Hence, with the expansion of grid 1, due to heating during service, vertical movement of the pins with respect to the rigidly fixed grid supporting members is obtained. The arrangement of elements is such as to allow free vertical movement with respect to the resistor frame, but to restrict movement in the lateral and longitudinal directions.

Figure 6 is a longitudinal sectional view of grid supporting member 5. Member 5 consists of a bolt 13 supported by plastic insulators 14 and 15 mounted in holes 16 and 17 bored in end members 3 and 4. A ceramic insulating sleeve 18 insulates the bolt from the currentconducting parts. Mounted on the insulating sleeve 18 are the metallic pin retaining sleeves 19 insulated from each other by ceramic washers 20. Grooves 21, in the sleeves 19, restrain the pins 11 loosely mounted therein from longitudinal movement with respect to the frame, but allow vertical movement of the pins upon expansion and contraction of grid unit 1.

Also mounted on the insulating sleeve 18 are lead-in terminals 8 and 9, insulated from the pin retaining members by ceramic washers 22. Lead-in terminals 8 and 9 are welded to the ends of grid unit 1 at points 23 and 24. Ceramic washers 25 insulate contactors 8 and 9 from the metallic retaining sleeves 26. Ceramic washers 27 further insulate the entire unit from the retaining nuts 28. By tightening all the retaining nuts of the resistance structure, a rigid frame is obtained.

The operation of the invention is quite obvious. When electrical currents are applied to the grid unit 1 through terminals 8 and 9, the grid will heat up and expand in accordance with its inherent coefiicient of expansion. Since the pins 11 and 12 are not secured to the grid supporting members 5, 6 and 7, but are merely resting within grooves 21 in the pin-retaining sleeves 19, vertical movement of the pins 11 and 12 with respect to the resistance frame with expansion of the grid unit 1 is permitted. The fit of the pins 11 and 12, in cooperation with the grooves 21 in the grid supporting members 5, 6, and 7, is such as to prevent lateral and longitudinal movement of the pins with respect to the resistance frame 2. Upon cooling of the grid unit 1 the grid will contract and pins 11 will move downwardly with respect to grid supporting members 5 and 6.

Thus it is seen that the invention provides a novel and secure means for connecting a resistor unit to a mounting frame while simultaneously allowing, in said connection,

for expansion and contraction of the grids and for any tendency toward misalignment of the grids of the resistor bank. 1

While I have shown and described one form of my invention, I desire that it be regarded merely asuillustrative. There will, obviously, be many other modifications within the scope of the appended claim. For instance, the resistance structure could be modified to include two or more grid supporting members secured to the end members near the top portions thereof, and two or more grid supporting members connected to the end members near the lower portions thereof, in order that the resistor grid might be freely supported within the frame.

What I claim is:

An electrical resistance structure comprising'a pair of end members, upper and lower resistor grid supporting members rigidly connecting said end members to form a frame, two of said supporting members being connected to said end members in spaced parallel relationship in a horizontal plane near the upper edges of said end members, one of said supporting members being connected to said end members near the lower edges of said end members, said supporting members having longitudinally spaced grooves, a resistor, grid unit, said grid unit comprising an element which is reversely directed upon itself within the plane of the frame and between its terminals to form a zig-zag resistor, and longitudinally spaced pairs of projecting upper and lower guide pins secured to the reversely directed portions of the grid adjacent the upper and lower grid supporting members of the frame, said upper guide pins being slidably cooperative on their outer surfaces with the inner adjacent portions of said grooves of said upper supporting members, and said lower guide pins being slidably cooperative on their opposed inner surfaces with the outer portions of said grooves of said lower supporting member, whereby said grid may expand or contract transversely of the frame upon variation of temperature of said grid.

References Cited in the file of this patent UNITED STATES PATENTS 1,569,415 Woodson Jan. 12, 1926 1,755,350 Fahrenwald Apr. 22, 1930 2,162,030 Piazzoli June 13, 1939 2,256,727 Sloane Sept. 23, 1941 2,662,958 Flight et a1. Dec. 15, 1953 2,680,178 Kuhn et al June 1, 1954 2,702,332 DuBois Feb. 15, 1955 2,740,033 Perrine et al. Mar. 27, 1956 

